Method of reducing signalling overhead and power consumption in a wireless communication system

ABSTRACT

A method of transmitting channel quality information (CQI) to an access network (AN) in a system having at least one carrier is disclosed. More specifically, the method includes receiving at least one packet from the AN, each of which includes an indicator, wherein the indicator provides buffer level information and ceasing transmission of the CQI of at least one non-anchor carrier to the AN if the buffer level information indicates that there is no more packet to be transmitted to an access terminal (AT).

This application claims the benefit of U.S. Provisional Application No.60/719,361, filed on Sep. 21, 2005, and U.S. Provisional Application No.60/721,312, filed on Sep. 27, 2005, which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of reducing signalingoverhead, and more particularly, to a method of reducing signalingoverhead and power consumption in a wireless communication system.

2. Discussion of the Related Art

In a multiple access communication system, communications between usersare conducted through one or more base stations, also referred to as anaccess network (AN). Here, multiple access refers to simultaneoustransmission and/or reception. Several multiple access techniques areknown in the art, such as time division multiple access (TDMA),frequency division multiple access (FDMA), amplitude modulation multipleaccess and code division multiple access (CDMA).

In general, multiple access communication system can be wireless orwired and can carry voice and/or data. An example of a communicationsystem carrying both voice and data is a system (e.g., CDMA2000) inaccordance with the IS-95 standard and a system conforming to the 3^(rd)Generation Partnership Project 2 (3GPP2).

As a part of CDMA2000 digital wireless standards 1xEV-DO stands for 1xEvolution Data Only or 1x Evolution Data Optimized. 1xEV-DO providessignificantly faster data rates with air interface speeds of up to4.9152 Mbps in a forward direction and up to 1.8432 Mbps in a reversedirection. 1xEV-DO Revision 0 only address data—not voice, but now,1xEV-DO Revision A and B can support voice. A system structure of1xEV-DO is illustrated in FIG. 1. Further, FIGS. 2 and 3 illustrate1xEV-DO default protocol architecture, and 1xEV-DO non-default protocolarchitecture, respectively.

In the conventional system, signals that make up overhead aretransmitted and received on a regular basis. By reducing unnecessarysignals, the system can operate more efficiently, resulting in lowerpower consumption at each terminal.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a method of reducingsignaling overhead and power consumption in a wireless communicationsystem that substantially obviates one or more problems due tolimitations and disadvantages of the related art.

An object of the present invention is to provide a method oftransmitting a channel quality information (CQI) to an access network(AN) in a multi-carrier system.

Another object of the present invention is to provide a method oftransmitting information to an access network (AN) in a multi-carriersystem.

A further object of the present invention is to provide a method oftransmitting packet in a multi-carrier system having at least onenon-anchor carrier, each of which has ceased transmitting channelquality information (CQI).

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, amethod of transmitting channel quality information (CQI) to an accessnetwork (AN) in a multi-carrier system includes receiving at least onepacket from the AN, each of which includes an indicator, wherein theindicator provides buffer level information and ceasing transmission ofthe CQI of at least one non-anchor carrier to the AN if the buffer levelinformation indicates that there is no more packet to be transmitted toan access terminal (AT).

In another aspect of the present invention, a method of transmittinginformation to an access network (AN) in a multi-carrier system includestransmitting an acknowledgement (ACK) signal to a received packet fromthe AN, activating a timer upon transmitting the ACK signal to the AN,and ceasing transmission of a channel quality information (CQI) of atleast one non-anchor carrier if the timer expires.

In further aspect of the present invention, a method of transmittingpacket in a multi-carrier system having at least one non-anchor carrier,each of which has ceased transmitting channel quality information (CQI)includes if at least one packet is buffered on an anchor carrier in anaccess network (AN), transmitting at least one packet and an indicatorfrom the AN on the anchor carrier, and if the at least one packet isbuffered on a non-anchor carrier in the AN, transmitting the at leastone packet and the indicator from the AN on at least one of the anchorcarrier or the non-anchor carrier. Here, the indicator can be set to ‘0’for the non-anchor carrier to maintain ceased transmission of the CQI orcan be set to ‘1’ for the non-anchor carrier(s) to begin CQItransmission.

In another aspect of the present invention, a method of transmittinginformation to an access network (AN) in a system having at least onecarrier includes receiving at least one packet from the AN at least onecarrier, each packet includes an indicator which provides buffer levelinformation, transmitting an acknowledgement (ACK) signal to a receivedpacket from the AN, activating a timer upon transmitting the ACK signalon the at least carrier, and ceasing transmission of the CQI of at leastone non-anchor carrier to the AN on the at least one carrier if thebuffer level information indicates that there is no more packet to betransmitted to an access terminal (AT) or if the timer expires.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings;

FIG. 1 illustrates a system architecture of 1xEV-DO;

FIG. 2 illustrates a 1xEV-DO default protocol architecture;

FIG. 3 illustrates a 1xEV-DO non-default protocol architecture;

FIG. 4 illustrates a possible problem caused by a round trip delaybetween the BSC and the BTS;

FIG. 5 illustrates a configuration of a multi-user packet (MUP) having aPacketInfo field of a reserved MAC index and a length (0) field; and

FIG. 6 shows another configuration for LPI in a MUP.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

In current systems, which tend to be single-carrier systems, anacceptable amount of overhead and power consumption is often incurred.In a multi-carrier system, it can be expected that significantly greateroverhead and power consumption would be incurred per terminal. Withincreasing demand for more and faster data transmission, similarpotential problems can be experienced by most wireless systems, and inparticular, 3^(rd) Generation Partnership Project (3GPP), 3GPP2, andOrthogonal Frequency Division Multiplexing (OFDM)-based systems.

By reducing signaling overhead in multi-carrier systems, batteryconsumption can be reduced. That is, by reducing transmit power and/orsignal processing requirements at the receiving end, battery consumptioncan be reduced. Here, signaling overhead refers to channel qualityinformation (CQI) feedback transmitted from an access terminal (AT) toan access network (AN), for example. In addition, reduction of signalingoverhead can reduce interference levels, in turn, increasing systemcapacity.

To this end, reducing signaling overhead can be described in two parts.In Part 1, a shared common signaling scheme from the AN to a scheduledAT is described. In Part 2, buffer level information at the AT for theAN to AT link is described. As such, the descriptions related to theembodiments of the present invention can be applied a communicationsystem having a single carrier as well as a system having multiplecarriers.

In Part 1, the AN transmits data packets to the scheduled AT. Thescheduled AT refers to an AT which receives designation-specific datapackets from the AN. For example, if the data packets are designated forAT#3, the AN sends these data packets to AT#3 and not to other ATs.

With each data packet transmitted to a scheduled AT, buffer levelinformation can be included or appended to the data packet. In otherwords, the AN can append information of a number of data packet(s) in aqueue for the scheduled AT and transmit this information with the datapacket to the scheduled AT. Here, the number of data packets in thequeue or the buffer level information refers to a number of data packetswhich are to be delivered to the scheduled AT by the AN. The bufferlevel information can also be referred to as buffer status information.

There are a number of ways for conveying the buffer level/statusinformation to the AT. In detail, transmission of the buffer levelinformation from the AN to the AT can be accomplished using a singlebit. The single bit can be used as an indicator to indicate whether thebuffer for the scheduled AT is empty or not empty. Empty buffer meansthat there is no data packets to be sent to the scheduled AT.Alternatively, non-empty buffers means that there is at least one datapacket to be transmitted to the scheduled AT.

The single bit for indicating the buffer level information can bereferred to as a last packet indicator (LPI) which applies to datapackets or non-anchor carriers. The non-anchor carrier is a carrierwhich carries data packets. The LPI is attached or appended to eachforward link (FL) data packet transmitted to the scheduled AT. Forexample, the LPI can be represented by either ‘0’ or ‘1’ to indicateempty or not empty status of the buffer, respectively. Here, the LPI of‘0’ (i.e., LPI=0) indicates that there are no more data packets for thescheduled AT on this particular non-anchor carrier. Alternatively, theLPI of ‘1’ (i.e., LPI=1) indicates that there are still more packets onthis particular non-anchor carrier for the scheduled AT. By using atleast two (2) bits, the granularity of the buffer level quantization canbe generalized to include fine or coarse quantization. Furthermore, byusing a single bit, signaling overhead can be minimized.

Alternatively, the LPI can be represented by 2 or more bits. Forexample, if 2 bits are used, these 2 bits can be used to denote fourbuffer levels, namely, empty, between empty and quarter full, betweenquarter full and half full, or between half full and full. Here, thenumber of packets in a full buffer can be configured and determined atstart-up.

Alternatively, in order to save transmission power for the AN and reduceinter-cell interference, LPI information can be transmitted using ON-OFFKeying. For example, ‘ON’ could indicate LPI=TRUE where as ‘OFF’ couldindicate LPI=FALSE.

Further, the buffer level information represented by the LPI can be madeinto a command. For example, if using a single bit, LPI=0 commands thescheduled AT to discontinue or cease transmission of the CQI since thereare no more data packets for the scheduled AT and for the particularcarrier on which the LPI was transmitted.

Using the LPI, single bit, or multiple bits to notify the scheduled ATthat there are no more data packets in the buffer can be interpreted asan indication to de-activate the CQI transmission or CQI reporting onnon-anchor carriers. Here, de-activation can indicate to the AT totransmit the CQI for a minimum number of forward link (FL) channels(e.g., 1). Conversely, activation can indicate to the AT to transmit theCQIs for the maximum number of configured FL channels (e.g., 3 channelsout of possible 16 channels). Regardless of the minimum number of CQItransmissions on non-anchor carrier, the AT maintains CQI transmissionof control packet on an anchor carrier. The details of activation of theCQI transmission will be discussed later.

In Part 2, the scheduled AT sends the CQI to the AN. For example, theCQI can be a data rate control (DRC), transmitted to help the AN todetermine the data rate for when scheduling ATs, rate control, and otherfunctions, In High Speed Downlink Packet Access (HSDPA) and 1x Evolutionfor Data and Voice (1xEV-DV) environments, the CQI represents roughlythe received signal-to-noise ratio (SINR) which is measured by the AT.

In current 1xEV-DO systems, the CQI is always transmitted in acontinuous or a gated fashion. The idea behind Part 2 is to transmit theCQI only when necessary. As described above, the CQI providesinformation on condition of a forward link (FL), from AT to AN, and inthis information, the DRC can be included.

To transmit the CQI or DRC only when necessary, the buffer levelinformation of Part 1 is applied. More specifically, the scheduled ATcan cease transmission of the CQI on non-anchor carriers to the AN afterreceiving the buffer level information indicating that there are no moredata packets for the scheduled AT (e.g., LPI=0) from the AN. Again,here, the non-anchor carriers refer to carriers that are used to carrydata packets, and an anchor carrier refers to one of N number ofcarriers which is used to carry control packet(s). The anchor carriercan also be referred to as a primary carrier or an anchor RL carrier.

As referred to above, the CQI or DRC reporting does not necessarily haveto be ceased for all non-anchor carriers. That is, the DRC reporting canbe active for a specific number of non-anchor carriers. In other words,the scheduled AT can continue to transmit the CQI on the anchor carrierand/or certain non-anchor carriers. It is imperative that the anchorcarrier remains active for the AT so that the AT can continue to monitorat least one FL channel for any FL packets for the AT and to possiblyreceive a command to activate all non-anchor carriers.

For finer quantization, the buffer level information can be used by theAT to determine a number of the CQI carrier channels. Here, the numberof CQI carrier feedback channels can be varied by the AT. That is, inaddition to using an anchor carrier, non-anchor carriers can also beused.

When the AN sends the LPI with a last packet indicating that there areno more packets for the AT, which can be interpreted as a command tostop reporting of the CQI over the non-anchor carriers, the AN may needto inform a base station control (BSC) of the AN so that the BSC may, inturn, inform all the sectors in the AT active set to let the other BTSsof the active set to expect to no longer receive the non-anchor CQIs.

In operation, the AT waits until all the LPIs are received from allnon-anchor carriers before ceasing or deactivating reception of datapackets from the AN (i.e., FL reception) and transmission of the CQI tothe AN on all the RL carriers, for example. However, as discussed above,it is important that a FL/RL anchor carrier remains active. That is,since the CQI for the FL carriers are needed to power control forwardlink control channels including the reverse link power control (RPC) andRL automatic repeat request (ARQ) ACK channels (carrying ACKs or NACKs)for the AT, the CQI reporting to the AN should not be discontinued.

If all the RPC and acknowledgement (ACK) channels for each RL channel iscarried on a single carrier ‘x,’ then only one CQI is needed. This meansthat the CQI for the other carriers can be turned off. As such, there isno need to use the CQI for other carriers to power control the RPC powerlevel and the ACK channel power level. A detailed description of the RPCand ACK channels is as follows.

Assume that there are N number of FL carriers and M number of RLcarriers. If the RPC and ACK channels for each RL is carried on aseparate FL carrier and N=M, then none of the CQI's can be turned off Ifthe RPC and ACK channels for each RL is carried on a separate FL carrierand N>M, then N number of CQIs are needed normally but only M number ofRPCs and ACK channels need power control. The minimum number of carriersfor which CQI must be reported is M. If the RPC and ACK channels foreach RL is carried on a separate FL carrier, N<M, and all N number of FLcarriers carry RL RPC and ARQ channels for the AT, then none of the CQIscan be turned off. Here, the CQI can be a DRC.

In addition to using an LPI for CQI transmission de-activation, the ATcan implement a timer function to determine whether to continue CQIreporting to the AN. First, a timer can be used to determine whether tocontinue or cease transmission of the CQI after all LPIs are receivedfor non-anchor carriers. This can be referred to as explicit buffersignaling. Second, a timer can be used to determine LPI based on thelast CQI sent or the last packet received. This can be referred to as animplicit buffer signaling. Lastly, a combination of the explicit and theimplicit buffer signaling can be implemented.

The following is a discussion of an explicit buffer signaling. When anLPI is received on a particular carrier, the AT maintains an openchannel for that particular carrier and can continue to provide the CQIof that particular carrier to the AN using the anchor RL carrier. Withinsertion of the timer function, a timer (or explicit timer) can beincorporated to allow continued communication between the AT and the ANfor a specified duration after all the LPIs are received for thenon-anchor carriers. That is, the timer at the AT can be initiated oncethe LPIs from all the non-anchor carriers are received. This would allowde-activation of the CQI transmissions after the timer has expired. Forexample, the timer can be set for 40 msec and if no packet is receivedbefore the expiration of 40 msecs, the AT can determine that there areno more scheduled packets and cease the CQI reporting. By configuringand implementing a timer, state signaling between a base station control(BSC) of the AN and a base transceiver station (BTS) of the AN can becorrectly synchronized first before the AT enters this de-activationmode.

Alternatively, as a discussion of an implicit buffer signaling, the LPIcan be determined for a two-state (e.g., empty and not empty bufferlevel) LPI indication. If a data packet is not received by the AT afterconfigurable time duration (e.g., 200 msec), then the AT can assume thatthere are no more packets to be sent by the AN, in turn determine thatthe buffer level is empty (e.g., LPI of ‘0’). Here, the timer (orimplicit timer) is configured by the AT for the specified time duration.At the same time, the AN can have a similar timer to make sure that thestates are synchronized between the BSC and the BTS.

In practice, the implicit timer can be initiated after sending the CQIto the AN. If more than one CQI is transmitted to the AN, the timer isreset and restarted after each CQI transmission. Alternatively, thetimer can be started after receiving a packet from the AN. If the ATreceives more than one packet, the timer is reset and re-started when asubsequent packet is received. In addition, the timer can be initiatedafter a specified time duration has expired after sending the CQI orafter receiving a packet. This means that the operation of the timer canbe configured by various means.

Next, the timer functions (i.e., explicit timer and implicit timer) ofabove can be applied in combination. That is, the explicit timer can beinitiated after all the packets are received, and the implicit timer canbe initiated after sending the CQI or receiving the packet.

In a multi-carrier system, the BSC of the AN can send packets on a partof the carriers and does not have to utilize all the carriers. In otherwords, the AN can send packets on M number of carriers out of Ncarriers, where M<N. For example, the AN can send packets only to threeof the four carriers. As such, the carrier without any packets for aparticular AT is not able to send an LPI, which is an indicator attachedto a FL packet to the AT. Therefore, the AT is unable to initiate animplicit timer since no CQI is reported. In this case, the AT and the ANcan set to use implicit signaling. On the other hand, when a packet issent to the AT on a particular carrier, the implicit timer is disabledand the explicit timer is used. Moreover, an explicit timer at the ATcan be initiated after all LPIs from all the active carriers arereceived. This allows de-activation of the CQI transmission after thetimer has expired.

At the AN, a scheduler of the AN can be made aware of the implicit timerso that it would be constrained to send at least one packet to an ATbefore the expiration of the timer and to initiate the explicitsignaling.

As discussed above, the AN can have a similar timer to make sure thatthe states are synchronized between the BSC and the BTS. FIG. 4illustrates a possible problem caused by a round trip delay between theBSC and the BTS. When there are no more packets for the AT and the timerexpires, all DRC transmissions for non-anchor FL carriers arediscontinued, and the AT stops monitoring data portion of the non-anchorcarrier. At the AN, the BTS sends a notification to stop sending data tonon-anchor carrier since the DRC transmission has ceased to the BSC.However, as shown in FIG. 4, if the BSC transmits new data to thenon-anchor carrier because it has not yet received the notification fromthe BTS, then a problem can arise. In order to prevent this time offsetor round trip delay, a BTS-BSC timer value can be configured to belarger than the round trip delay between the BTS and the BSC.

If the timer (e.g., explicit timer or implicit timer) is initiated andis expired after configured time duration, as discussed above, the ATstops the CQI transmission to the AN. In this situation, since the AT nolonger sends the CQI/DRC, the state of the AT can be said to be in a‘sleep’ state. When the timer expires, the BTS of the AN is also awareof the fact that there are no packets buffered for the AT. As such, theBTS sets itself to not expect to receive any CQIs or DRCs (e.g.,DRC_on=0).

However, during the sleep state, the BTS can receive packets for the AT.To receive these packets from the AN, the AT has to wake up andterminate the sleep state to receive the packets. The details of how theBTS can wake up the AT will be provided below. After the scheduled AThas completed receiving the scheduled packet(s), the timer isre-started. Alternatively, the timer can be re-started after receipt ofeach packet from the AN.

In order for the AN to wake up the AT from its sleep state, a wake-upindicator (WUI) or a first packet indicator (FPI) can be designed andsent to the AT to re-start the CQI transmission. As discussed above, thesleep state refers to no transmission of the CQIs since there are nopackets to be delivered on the carriers. However, when there are packetsto be transmitted by the AN while the AT is in sleep mode, the AN canwakes up or notify the AT that there are packets to be sent Thisnotification is made by the WUI or the FPI.

In detail, the AN sends the WUI to a particular AT. Here, the WUI can besent on the anchor carrier or the non-anchor carrier. As discussedabove, the anchor carrier is always connected, whereas the non-anchorcarriers are not. However, for the purpose of delivering the WUI, eithercarrier type can be used.

As a method of indicating the WUI, a LPI can be used. In other words,the signaling of the WUI can be done in a variety of ways. First, thesignaling can be executed using a two-state bit indicating either LPI orWUI. For example, a bit of ‘0’ could be used to represent the LPI, and abit of ‘1’ could be used to represent the WUI. Alternatively, a separatebit for signaling WUI can be used. Here, the bit indicating either theLPI or the WUI is appended to a packet scheduled to a target AT.

More specifically, when the AT receives the LPI on an anchor carrier,the AT can interpret the LPI as WUI and sets the CQI reporting tocontinue on all non-anchor carriers (DRC_on=1). Thereafter, the AT canstart transmitting the CQI (or DRC) on all non-anchor carriers At thesame time, the AN sets (DRC_on=1) to receive the CQI reporting on allnon-anchor carriers.

Alternatively, without a packet to send to the AT, the LPI cannot besent. However, this problem can be resolved by sending a dummy packet tothe AT using a multi-user packet format in order to make the AT starttransmitting the CQI before transmitting real new packets. The detailsof the multi-user packet (MUP) format will be discussed later. The ATalways monitors pilot/MAC portion on all assigned carriers even thoughthe AT stops transmitting the CQI on certain or all non-anchor carriers.When the AT receives a dummy packet with the LPI attached thereto fromon the non-anchor carrier, the AT discards the dummy packet and sets theCQI reporting to continue on all non-anchor carriers (DRC_on=1). At thesame time, the AN sets (DRC_on=1) to receive the CQI reporting on allnon-anchor carriers.

Furthermore, the LPI or the WUI can be transmitted over a null-ratepacket. This transmission over the null-rate packet can be for signalingpurposes. The AN can use the null-rate packet to indicate that the ATshould wake up and begin transmitting the CQIs. Alternatively, the ANcan use a separate signal to indicate that the AT should activate theCQI transmission. For example, this could be done by sending aDRC_LOCK_ON/OFF signal over a configured number of consecutive ornon-consecutive transmissions from all sectors in the AT active set.

It is possible to have each carrier indicate to some central processingunit when the WUI (or LPI) is sent. This central processing unit can actas a contact point for the BSC of the AN.

In addition, the AN can send an activate indicator (ACTI) to the AT. TheACTI applies to an anchor carrier. Moreover, the ACTI can be representedusing one (1) bit. For example, if the ACTI is represented by ‘1’ (i.e.,ACTI=1) on an anchor carrier, this indicates that all non-anchorcarriers are to be activated or waken up. That is, the AN commands theAT to activate the non-anchor carriers since there are data packets forthe AT. On the other hand, if the ACTI is represented by ‘0’ (i.e.,ACTI=0) on an anchor carrier, this indicates that the non-anchorcarriers should remain de-activated since there are no scheduled datapackets for the AT.

If data for AT is received at the buffer of the anchor carrier by theBTS of the AN when the CQI (or DRC) is not being reported (e.g.,DRC_on=0), the BTS follows an instruction from the BSC of the AN toeither send packets on the anchor carrier with ACTI=0 or send packets onthe anchor carrier with ACTI=1, thus activating all non-anchor carriers.

Alternatively, if newly arrived data for AT is received at the buffer ofa non-anchor carrier by BTS when the CQI (or DRC) is not being reported(e.g., DRC_on=0), then the AN tries to send a packet on the non-anchorcarrier if the CQI/DRC is still reported on the non-anchor carrier.However, if the CQI/DRC is not reported for the non-anchor carrier andthere are packets for the AT buffered at the anchor carrier, then the ANsends a packet on the anchor carrier with ACTI=1, thus activating allnon-anchor carriers. Here, initially, all non-anchor FL carriers cannottransmit packet to the AT since there are no DRCs for them. The AT onlylistens to the anchor carrier, By sending a packet with ACTI=1 on theanchor carrier to the AT, the AT realizes that it is time to startreporting the DRCs for other non-anchor carriers. Hence, the AN canstart transmitting packets on the non-anchor carriers.

If activation of CQI/DRC reporting is selected, the BTS sets activationto begin receiving the CQI/DRC from the AT. After the BTS of the AN hasset activation and the first packet can be transmitted by the AN, the ANcan add all non-anchor FL carries to the set of carriers for whichDRCLock value is determined. Here, DRCLock represents the quality of theDRC. A timer, which serves as an implicit LPI, for each non-anchorcarrier, except for the one which sent the packet is started. Within theAN, the BTS sends a message to the BSC to inform that it is ready toreceive data on all non-anchor carriers. After the AN sends a packet onthe non-anchor carrier, the implicit LPI timer, associated with thecarrier and the AT, can be stopped. If the explicit LPI is used, thetimer should not be restarted. Lastly, if the implicit LPI timer isactive and there is FL packets buffered, the scheduler of the carriercan schedule one of the packets before the timer expires.

If a packet is received on a non-anchor carrier or on an anchor carrierwith ACTI=1 when the CQI reporting is de-activated, the AT can configureto start CQI/DRC reporting to the AN. Thereafter, the AT startsreporting DRCs for all non-anchor carriers, and at the same time, atimer for each non-anchor carrier, which serves as an implicit LPI, iscan be started. If the BST-BSC timer of the AN is active at this time,the timer can be turned-off.

Further, the ACTI can be represented by more than a single bit. The ACTIof two (2) bits, for example, can be used to notify the AT to activate apart of the non-anchor carriers. For example, the ACTI of 2 bits denotesfour levels, and as such, one of the levels can command the AT toactivate a half of the non-anchor carriers while another level cancommand the AT to activate three quarters of the non-anchor carriers.Based on the number of bits used to represent the ACTI, the command fromthe AN to the AT can be more specific.

Following is a description of a single-user packet and a multi-userpacket. Since the LPI and the ACTI can be sent using same mechanism, thefollowing description will be made using the LPI.

With respect to a single-user packet a Walsh code, having a length of128, can be reserved for transmitting the LPI to an AT for a carrierwhich does not carry an RPC and RL ARQ channels for the AT. Here, theWalsh code is not used for a medium access channel (MAC) multiplexing(e.g., MAC index 67, W¹²⁸ ₉₇). When a FL packet is sent and there is nodata buffered for the AT on this particular carrier, the LPI indicationbit can be sent on RPC/RL ARQ channel of the carrier covered with theWalsh code associated with the reserved MAC index. After the packet issent and there is no data in the buffer for the AT on the carrier, theAN can set de-activation CQI/DRC transmission from the AT. For example,the AN can set DRC_(off)=1 to indicate that there are no more CQI or DRCreporting from the AT. After the AT receives the packet with the LPI,the AT sets DRC_(off)=1.

With respect of a multi-user packet (MUP), the AN places a PacketInfofield and length fields of the ATs, having the last packet in this MUP,at the beginning of the packet header section. Alternatively, the ANplaces PacketInfo fields and length fields of the AT, having morepackets to deliver in this MUP, at the end of the packet header section.The fields associated with the last packet and more packets areseparated by a PacketInfo field of a reserved MAC index and a length (0)field. The length (0) field indicates a demarcation point. That is, whenthe AT's PacketInfo is located before the length (0) field, then the LPIis indicated. Alternatively, when the AT's PacketInfo is located afterthe length (0) field, then this indicates that there are still morepackets to be sent, and the LPI is not indicated. FIG. 5 illustrates aconfiguration of a multi-user packet (MUP) having a PacketInfo field ofa reserved MAC index and a length (0) field. In the packet, LPI forseveral ATs may be included.

FIG. 6 shows another configuration for LPI in a MUP. In this figure, abitmap is appended at the end of the payloads to indicate which packetinside the MUP is a last packet. This location of the bitmap causes alegacy AT to believe that the bitmap is part of a pad field. Inaddition, a bit covered by the reserved MAC index sent on RPC/RL ARQchannel can be used to indicate if the LPI map is included in the MUP.

It is possible for the AT to stop reporting the CQI or DRC fornon-anchor carriers while the AN still has packets to send. This couldoccur, for example, when the LPI is falsely detected for the lastcarrier with packets. In this situation, the last carrier still needs tosend packet(s) to the AT but the CQI for the last carrier is no longeravailable.

Here, if the AT stops reporting the DRC for non-anchor carriers (e.g.,DRC_on=0) but the AN still has packets to send (e.g., DRC_on=1), the ANmay use the packet sent to the AT on anchor carriers with a ACTI=1 toinform the AT to resume reporting the DRC for non-anchor carriers.

Alternatively, the DRCLock channel on the anchor carrier can also beused to avoid the above situation. If the AT observes DRCLock for aspecified period (e.g., three consecutive reports), the AT can set toreport DRCs (e.g. DRC_on=1) for all non-anchor FL carriers. The AT thencan begin reporting the DRCs for all non-anchor carriers.

On the contrary, the AT may still think that there are packets toreceive when the AN actually has no packets to send. This is possible ifan LPI were missed. Here, the communication system can still function,but the AT cannot take advantage of the savings from gating thenon-anchor DRCs. To correct the misinterpretation by the AT, the AN caninclude a PacketInfo field of the AT and a length field with value zeroin a MUP, as shown in FIGS. 5 and 6, to signal the LPI without sending apacket to the AT. Here, the MUP is intended for other ATs but includesthis particular AT as one of its recipients. This serves as a back-upLPI. Thereafter, the AT follows the normal procedure to discontinue theDRC for the carrier the MUP is sent on. As for the AN, the AN usuallyknows whether the AT is transmitting the DRC or not because there is analgorithm for generating the DRCLock. Here, the AN accumulates the DRCchannel energy for several slots (i.e., DRCLength) and determineswhether a valid DRC is received based on the amount of energy itreceives on the AT's DRC channel.

In the discussion of above, the AN transmits the LPI with the lastpacket to indicate that there are no more packets to follow.Alternatively, the AT can also send a RL LPI to notify the AN that therewill be no more reverse link transmission following the last packet.With this notification, the AT does not need to continuously send nullrate RRI after the last packet has been sent. As such, the AN does notneed to decode the RRI as well as the RL data. In turn, battery powercan be conserved at the AT.

In the discussion of above, the AT can also be referred to as a mobilestation, a mobile subscriber station, a terminal, a mobile terminal, anda like. Further, the AN can also be referred to as a node, a basestation, a base subscriber station, a base terminal, a base terminalstation, and a like.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A method of transmitting channel quality information (CQI) to anaccess network (AN) in a system having at least one carrier, the methodcomprising: receiving at least one packet from the AN, each of whichincludes an indicator, wherein the indicator provides buffer levelinformation; and ceasing transmission of the CQI of at least onenon-anchor carrier to the AN if the buffer level information indicatesthat there is no more packet to be transmitted to an access terminal(AT).
 2. The method of claim 1, wherein the buffer level information isrepresented by 1 bit.
 3. The method of claim 2, wherein the 1 bitindicates that either there is no more packet to be transmitted to theAT or there are more packets to the transmitted to the AT.
 4. The methodof claim 1, wherein the buffer level information is represented by atleast 2 bits.
 5. The method of claim 4, wherein the at least 2 bitsdenotes a number of buffer levels corresponding to the number that bitsrepresent.
 6. The method of claim 5, wherein a number of CQI carrierfeedback channels to be used is determined by the AT based on the numberof buffer levels.
 7. The method of claim 1, wherein the indicator is alast packet indicator (LPI) which indicates a buffer level for the AT.8. The method of claim 7, wherein the buffer level represents whetherthere is no more packets to be transmitted to the AT or there are morepackets to the transmitted to the AT.
 9. The method of claim 7, whereinthe LPI is included in a header portion of the packet in a multi-userpacket.
 10. The method of claim 7, wherein the LPI is appended at theend of a payload in a multi-user packet.
 11. The method of claim 7,wherein the LPI is in a bitmap format.
 12. The method of claim 7,wherein the LPI is a command.
 13. The method of claim 1, wherein the CQIrepresents a signal-to-noise ratio measured by the AT.
 14. The method ofclaim 1, wherein the CQI includes data rate control (DRC) information.15. The method of claim 1, wherein the non-anchor carrier is a carrierused for data transmission.
 16. A method of transmitting information toan access network (AN) in a system having at least one carrier, themethod comprising: transmitting an acknowledgement (ACK) signal to areceived packet from the AN; activating a timer upon transmitting theACK signal to the AN; and ceasing transmission of a channel qualityinformation (CQI) of at least one non-anchor carrier if the timerexpires.
 17. The method of claim 16, wherein the non-anchor carrier is acarrier used for data transmission.
 18. The method of claim 16, whereinthe CQI includes a data rate control (DRC).
 19. A method of transmittingpacket in a system at least one carrier which is represented by at leastone non-anchor carrier, each of which has ceased transmitting channelquality information (CQI), the method comprising: if at least one packetis buffered on an anchor carrier in an access network (AN), transmittingat least one packet and an indicator from the AN on the anchor carrier;and if the at least one packet is buffered on a non-anchor carrier inthe AN, transmitting the at least one packet and the indicator from theAN on at least one of the anchor carrier or the non-anchor carrier. 20.The method of claim 19, wherein the anchor carrier is a channel used fortransmitting control information.
 21. The method of claim 19, whereinthe non-anchor carrier is a carrier used for transmitting datainformation.
 22. The method of claim 19, wherein the indicator set to‘0’ represents the non-anchor carriers to maintain ceased transmissionof the CQI, and the indicator set to ‘1’ represents activating thenon-anchor carriers to begin transmission of the CQI.
 23. The method ofclaim 19, wherein if the at least one packet is buffered on thenon-anchor carrier and the CQI is reported for the non-anchor carrier,the AN transmits the at least one packet on the non-anchor carrier. 24.The method of claim 19, wherein if the at least one packet is bufferedon the non-anchor carrier and the CQI is not reported for the non-anchorcarrier, the AN transmits the at least one packet on the anchor carrierwith the indicator set to ‘1.’
 25. The method of claim 19, wherein theindicator set to ‘1’ represents activating the non-anchor carriers tobegin transmission of the CQI.
 26. A method of transmitting informationto an access network (AN) in a system having at least one carrier, themethod comprising: receiving at least one packet from the AN at leastone carrier, each packet includes an indicator which provides bufferlevel information; transmitting an acknowledgement (ACK) signal to areceived packet from the AN; activating a timer upon transmitting theACK signal on the at least carrier; and ceasing transmission of the CQIof at least one non-anchor carrier to the AN on the at least one carrierif the buffer level information indicates that there is no more packetto be transmitted to an access terminal (AT) or if the timer expires.